TCP delayed acknowledgment is a technique used by some implementations of the Transmission Control Protocol in an effort to improve network performance.
If the sender does not send enough data to fill the maximum segment size (for example, if it performs two small writes followed by a blocking read) then the transfer will pause up to the ACK delay timeout.
Bob's socket layer has less than a complete packet's worth of data remaining to send.
If the application is transmitting data in smaller chunks and expecting periodic acknowledgment replies, this negative interaction can occur.
To prevent this delay, the application layer needs to continuously send data without waiting for acknowledgment replies.